package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Slf4j
@Component
public class CacheClient {
    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }
    public void set(String key, Object value, Long time, TimeUnit unit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit) {
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)) );
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }
    public <R,ID>R queryWithPassThrough(String keyPrefix, ID id, Class<R>type, Function<ID,R>dbFallback,Long time, TimeUnit unit) {

        String key = keyPrefix + id;
        //1.从Redis查询商户缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isNotBlank(json)) {
            //3.存在则直接返回
            JSONUtil.toBean(json, Shop.class);
            return   JSONUtil.toBean(json, type);
        }
        //判断命中是否为空值
        if(json!=null) {
            return null;
        }
        //4.不存在则根据id查询数据库
        R r= dbFallback.apply(id);
        //模拟高并发时的重建延迟

        //5.不存在，将空值写入redis
        //返回错误信息
        if(r==null) {
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }

        //6.存在，写入redis
       this.set(key,r,time,unit);
        //7.返回
        return r;
    }


   //定义一个线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
    public <R,ID>R queryWithLogicalExpire(String keyPrefix, ID id, Class<R>type, Function<ID,R>dbFallback,Long time, TimeUnit unit) {

        String key = keyPrefix + id;
        //1.从Redis查询商户缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isBlank(json)) {
            //3.不存在则直接返回空
            return   null;
        }
        //4.命中，需要把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        JSONObject data=(JSONObject) redisData.getData();
        R r= JSONUtil.toBean(data,type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())) {
            //5.1未过期，直接返回店铺信息
            return r;
        }

        //5.2已过期，需要缓存重建

        //6.缓存重建
        //6.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //6.2判断锁是否获取成功
        if(isLock){
            //6.3获取锁成功，开启独立线程实习缓存重建
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    //重建缓存
                    //先查数据库，再写redis
                    R r1 = dbFallback.apply(id);
                    this.setWithLogicalExpire(key, r1, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unLock(lockKey);
                }

            });
        }

        //6.4返回过期商铺信息
        return r;

    }

    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", LOCK_SHOP_TTL, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);

    }
    private void unLock (String key){
        stringRedisTemplate.delete(key);
    }
}
